Add Key Colors target type for extracting colors from screen regions

Introduce a new "key_colors" target type alongside WLED targets, enabling
real-time color extraction from configurable screen rectangles with
average/median/dominant modes, temporal smoothing, and WebSocket streaming.

- Split WledPictureTarget into its own module, add KeyColorsPictureTarget
- Add KC target lifecycle to ProcessorManager (register, start/stop, processing loop)
- Extend API routes and schemas for KC targets (CRUD, settings, state, metrics, colors)
- Add WebSocket endpoint for real-time color updates with auth
- Add KC sub-tab in Targets UI with editor modal and live color swatches
- Add EN and RU translations for all key colors strings

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/wled_controller/storage/picture_target.py

@@ -1,12 +1,9 @@
-"""Picture target data models."""
+"""Picture target base data model."""
 
-import uuid
-from dataclasses import dataclass, field
+from dataclasses import dataclass
 from datetime import datetime
 from typing import Optional
 
-from wled_controller.core.processor_manager import ProcessingSettings
-
 
 @dataclass
 class PictureTarget:
@@ -14,7 +11,7 @@ class PictureTarget:
 
     id: str
     name: str
-    target_type: str  # "wled" (future: "artnet", "e131", ...)
+    target_type: str  # "wled", "key_colors", ...
     created_at: datetime
     updated_at: datetime
     description: Optional[str] = None
@@ -35,62 +32,9 @@ class PictureTarget:
         """Create from dictionary, dispatching to the correct subclass."""
         target_type = data.get("target_type", "wled")
         if target_type == "wled":
+            from wled_controller.storage.wled_picture_target import WledPictureTarget
             return WledPictureTarget.from_dict(data)
+        if target_type == "key_colors":
+            from wled_controller.storage.key_colors_picture_target import KeyColorsPictureTarget
+            return KeyColorsPictureTarget.from_dict(data)
         raise ValueError(f"Unknown target type: {target_type}")
-
-
-@dataclass
-class WledPictureTarget(PictureTarget):
-    """WLED picture target — streams a picture source to a WLED device."""
-
-    device_id: str = ""
-    picture_source_id: str = ""
-    settings: ProcessingSettings = field(default_factory=ProcessingSettings)
-
-    def to_dict(self) -> dict:
-        """Convert to dictionary."""
-        d = super().to_dict()
-        d["device_id"] = self.device_id
-        d["picture_source_id"] = self.picture_source_id
-        d["settings"] = {
-            "display_index": self.settings.display_index,
-            "fps": self.settings.fps,
-            "border_width": self.settings.border_width,
-            "brightness": self.settings.brightness,
-            "gamma": self.settings.gamma,
-            "saturation": self.settings.saturation,
-            "smoothing": self.settings.smoothing,
-            "interpolation_mode": self.settings.interpolation_mode,
-            "state_check_interval": self.settings.state_check_interval,
-        }
-        return d
-
-    @classmethod
-    def from_dict(cls, data: dict) -> "WledPictureTarget":
-        """Create from dictionary."""
-        from wled_controller.core.processor_manager import DEFAULT_STATE_CHECK_INTERVAL
-
-        settings_data = data.get("settings", {})
-        settings = ProcessingSettings(
-            display_index=settings_data.get("display_index", 0),
-            fps=settings_data.get("fps", 30),
-            border_width=settings_data.get("border_width", 10),
-            brightness=settings_data.get("brightness", 1.0),
-            gamma=settings_data.get("gamma", 2.2),
-            saturation=settings_data.get("saturation", 1.0),
-            smoothing=settings_data.get("smoothing", 0.3),
-            interpolation_mode=settings_data.get("interpolation_mode", "average"),
-            state_check_interval=settings_data.get("state_check_interval", DEFAULT_STATE_CHECK_INTERVAL),
-        )
-
-        return cls(
-            id=data["id"],
-            name=data["name"],
-            target_type=data.get("target_type", "wled"),
-            device_id=data.get("device_id", ""),
-            picture_source_id=data.get("picture_source_id", ""),
-            settings=settings,
-            description=data.get("description"),
-            created_at=datetime.fromisoformat(data.get("created_at", datetime.utcnow().isoformat())),
-            updated_at=datetime.fromisoformat(data.get("updated_at", datetime.utcnow().isoformat())),
-        )